One technical solution to address the problem posed could consist in implementing an electromagnet that is functionally associated with a return spring for returning the body to the stable first position. Exciting the electromagnet makes it possible to overcome the opposing force due to the spring and thus to move the body in translation towards the second position. The pre-stressing of the spring makes it possible to hold the body in the first position in the presence of loads smaller than said pre-stressing. As regards failing safely, the return spring spontaneously returns the body to the first position in the event that the power supply to the electromagnet is interrupted.
Unfortunately, that conventional solution lies in the fact that holding the body in the second position, which requires a constant supply of power corresponding to at least the power supply necessary for the electromagnet to overcome the force generated by the return spring as compressed, which does not satisfy the desire for the power supply to be minimized.
Another solution could consist in implementing a motor and gearbox unit associated with a screw-and-nut or geared transmission device in order to move the body in translation; the presence of a clutch device can procure the desired failsafe effect.
Unfortunately that other solution suffers from drawbacks. Motor and gearbox units suitable for transforming the movement in rotation of the motor into a movement in translation under a sufficient traction force do not make it possible to guarantee a travel time between the first and second positions that is as short as the travel time procured by an electromagnet. In addition, implementing a screw-and-nut transmission very significantly reduces the efficiency of the device. Furthermore, such a transmission is generally irreversible: in order to satisfy the failsafe constraint, it is then necessary to use a declutch device for declutching the screw or the nut in order to allow the body to return freely to the first position.
Under such conditions, if additional requirements are added, such as looking for a short stroke that is traveled in as short a time as possible, or looking for a device that occupies a rectangular block shaped space that is as small as possible, or indeed looking for power consumption that is as low as possible in order to remain compatible with a low power source that is shared with a plurality of other vital devices in an overall system, it can be understood that the above-mentioned conventional solutions can in no way satisfy the various and numerous requirements.
In order to give some idea, a particular but non-exclusive application of the invention lies in stabilizing an optronic load, such as a sight mounted on a vehicle in an environment that can be subjected to a large amount of vibration, with the direction of aim being held, and more precisely in stabilizing optronic sensors in which, at rest, the fine pins must be locked by a device that is compact and that does not consume much electrical power. In which case, the body to be moved is a locking member (finger, stud, or the like) belonging to a support or to the load to be locked, and suitable for being engaged in a recess belonging respectively to the load or to the support (first stable position that must be occupied in failsafe manner, for locking the load) or for being disengaged (second position, which is a held position, for releasing the load).